There are little to no retcons in the Shadowrun canon that mark earlier in-universe information wrong via out of universe means in later editions. This is not needed because quite a lot of the Meta-Plot is presented as "Shadowtalk", making any non-rule-section (or non-"behind the scenes" part of runs) of the book an in-universe text. As these are actually prone to be proven as faulty or biased, there is no real need to "retcon" parts of the universe. Sometimes they just reply with a clarification or a doubtful comment in other shadowtalk at the same time the original statement is published, but at times they just reference the old posts and call the posters names for behavior from earlier.
On a different scale are the campaign books that often paste in a "behind the scenes" snippet for GMs and Players that state exactly how it really is/was to make sure that the in-universe mention is/was not fully credible - and I know of none of these to be retconned up to now, only appended to, as in the case of Dunkelzahn's death.
If you want an example of one of these 'soft retcons' in one book: Take the SR4 Emergence plot, and compare the Shadowtalk/Media parts with the matter-of-factly "behind the scenes" parts that describe what really happened. You should quickly realize some of the "revelations" claimed by the talkers/media are hoaxes.
During these Plot-arcs (and in the history parts in the core books), the whole 'history' of the world gets pushed forwards, into the far future, always 60 years ahead and dominated by the megacorps...
Interestingly, technology in Shadowrun seems to evolve in a way to emulate what we have today plus some 60 years to keep it "up to date" with the futuristic look and feel.
One of the most noticeable examples is probably the Matrix: In the end of 3rd Edition, the first wireless computer networks came up in the real world and computers had become smaller than the typical C64-like Cyberdecks in SR1-3. So they mirrored the wireless connectors into the Shadowrun universe. Then, the first smartphones became popular just about the time SR4 was in planning. To justify an All-Wifi-Matrix (and get rid of old baggage) and make it all shiny cool, the 2nd Matrix Crash was put in between the 3rd and 4th edition. As a result, people ran around with ultra-hacker-smartphones (eh, comlinks). But As that seemed to have gone too far, SR5 was like a technological step back to more boxy Cyberdecks - but they justified it with some shenanigans about yet again fully new matrix protocols that had been established because of hacker and Technomancer fear.
